Abstract
Background/Objectives In this exciting era of exponential growth in targeted oncologic therapies, it is important to be mindful of the possibility of neurological immune-related adverse effects. We present a case of Guillain-Barré Syndrome (GBS) associated with binimetinib, a MEK inhibitor, and encorafenib, a BRAF inhibitor, for the treatment of metastatic melanoma.
Methods Single case report
Results A 60-year-old Caucasian man with metastatic melanoma developed progressive bilateral upper and lower limb weakness, dysphagia and paraesthesia and numbness in a ‘glove and stocking’ pattern over three weeks. This began eight months following commencement of binimetinib and encorafenib, and ten months following cessation of nivolumab due to acute interstitial nephritis. Contrast-enhanced magnetic resonance imaging of the brain and spine was normal. Cerebrospinal fluid protein was elevated at 2.2 g/L, white cell count was normal at 2 cells per microlitre and cytology was negative for malignant cells. Nerve conduction studies and electromyography were consistent with a polyradiculoneuropathy with axonal and demyelinating features. Binimetinib and encorafenib were ceased and intravenous methylprednisolone and immune globulin were administered for five days. There was resolution of dysphagia and moderate improvement in limb weakness over a six-month follow-up period.
Conclusion We present a case of GBS attributed to binimetinib and encorafenib. The mechanism behind this rare adverse effect remains uncertain, but may involve molecular mimicry: melanocytes and Schwann cells share a neuroectodermal origin and surface molecules, while BRAF and MEK inhibitors increase the immune response against melanoma. Awareness and early recognition of this condition are key to optimising outcomes.
